The embodiments of the present specification relate to impedance imaging, and more particularly to electrical impedance imaging.
In electrical impedance tomography, currents are injected through electrodes and corresponding voltages are measured at the electrodes to determine a resistivity distribution in an internal medium of a subject of interest. The measured voltages are representative of voltage drops along a current pathway. Also, the measured voltages may entail both an internal impedance of the internal medium and a contact impedance at an interface of an electrode and the subject of interest. It may be noted that the contact impedance exists at the interface between the electrode and a surface of the subject of interest. In one example, in the case of the electrode-skin contact, the contact impedance exists at an electrode-skin interface and may be referred to as electrode-skin contact impedance. In another example, in case of saline phantom studies, the contact impedance may exist in the form of electrode-electrolyte impedance. Moreover, an internal current density distribution in the subject of interest may be influenced by the contact impedance, thereby adversely affecting the impedance imaging.
Additionally, a voltage drop across the contact impedance is relatively large as compared to voltage drops across the internal impedance. Also, the electrode-skin contact impedance and/or the electrode-electrolyte impedance may change over time as the interface absorbs or desorbs fluids and/or ions.